Secure data exchange

ABSTRACT

A data transfer method performed at a proxy server includes intercepting a data request from a client computer that is directed to a target server, encrypting profile information, augmenting the data request by adding the encrypted profile information to the data request, and sending the augmented data request to the target server. A data transfer method that is performed at an information server includes receiving a data request from a proxy server, extracting profile information added to the data request by the proxy server, using the extracted profile information to generate a response, and sending the response to the proxy server.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/786,212, filed Mar. 5, 2013, titled “Secure Data Exchange BetweenData Processing Systems”, which is a continuation of U.S. patentapplication Ser. No. 13/030,986, filed Feb. 18, 2011titled “Secure DataExchange Between Data Processing Systems”, which is a continuation ofU.S. patent application Ser. No. 11/535,056, filed Sep. 25, 2006, titled“Secure Data Exchange Between Data Processing Systems”, now issued asU.S. Pat. No. 7,895,446, which is a continuation of U.S. applicationSer. No. 09/323,415, filed Jun. 1, 1999, titled “Secure Data ExchangeBetween Data Processing Systems”, now issued as U.S. Pat. No. 7,146,505,all of which are incorporated by reference.

BACKGROUND

FIG. 1 shows a computer network 100 that includes both client computers111-113 and server computers 131-133. The network 100 also includes dataconnections that allow the client computers to communicate with theservers. Those data connections include access connections 114-116, aservice provider's point of presence (POP) 110, network 120, proxyserver 117, and network 130. POP 110 includes data communicationsequipment that allows a client computer 111-113 to connect to thenetwork 120. For example, POP 110 may include dial-up modem banks, cablemodem banks, a T1 interface, wireless communications equipment, or otherdata transmission equipment.

After a client computer 111-113 has been connected to the network 120(through POP 110) it may exchange data with other computers on thenetwork 120. Computers on different networks 120 and 130 also canexchange data with each other by sending their data request to proxyserver 117 which, in turn, can forward their request to the destinationcomputer, obtain a response from the destination, and return theresponse to the requesting computer.

The servers 131-133 and clients 111-113 may communicate with each otherusing the hypertext transfer protocol (HTTP). HTTP is a datacommunications protocol that is used by web browser programs (such asMicrosoft Internet Explorer and Netscape Navigator) to communicate withweb server applications (such as Microsoft Internet Information Serverand Netscape Server). Thus, by executing a web browser, a clientcomputer 111-113 can exchange data with a server 131-133 that isexecuting a web server application.

When a web server receives a HTTP data request from a browser, a webserver application, such as a Common Gateway Interface (CGI) script, maybe used to query databases, customize responses, and/or perform otherprocessing used to generate a response. The web server application mayneed data about the client computer, the browser, its user, and/or otherdata in order to complete its processing of the data request. Forexample, a web server application may provide customized weatherinformation based on a user's home address. The web application mayobtain the user's address information by sending a data input form tothe browser and receiving a user's response that contains the neededinformation. A web server application also may obtain needed data fromweb server environmental variables that are populated by data in HTTPheader fields, by a web server, and/or by a web server sub-component.For example, a CGI script's response to a data request may depend on thetype of browser originating the request. The CGI script may access aHTTP environment variable (“HTTP_USER_AGENT”) populated by the webserver using data from a “User-Agent” field in a HTTP header. The valueof the HTTP_USER_AGENT variable identifies the type of browseroriginating a request so that the CGI script can customize its responseto that browser.

A web server and a browser also may exchange web cookies that containdata. A web cookie is data file that can be automatically exchangedbetween browsers and servers along with the request and responsesexchanged between the browsers and servers. When a web cookie isreceived by a browser, it can be stored at the client computer. Duringfuture transactions with the web server, the web cookie (and any datathat it contains) can be sent back to the web server. By using datastored in web cookies, a web server's need to request data from a usermay be reduced. However, since web cookies are typically stored on aclient computer, they may be deleted and their data lost. Furthermore,if a user moves to another computer, web cookie information stored onthe user's original computer will be unavailable to that user. Thesefactors may reduce the utility of web cookies.

The present inventors recognize that information service systems, suchas web servers, should provide convenient, secure, reliable, and simplemeans of interacting with users. The present inventors further recognizewhen a server must query a user for data or use web cookies for datastorage and input, convenience, security, reliability, and simplicitymay suffer. Consequently, the invention disclosed herein providesadditional means of providing information to a web server applicationthat may provide additional flexibility in implementing informationsystems.

SUMMARY

In general, in one aspect, the invention features a data transfer methodperformed at a proxy server. The method includes intercepting a datarequest from a client computer that is directed to a target server,encrypting profile information, augmenting the data request by addingthe encrypted profile information to the data request, and sending theaugmented data request to the target server. In another aspect, theinvention features a data transfer method performed at an informationserver. The method includes receiving a data request from a proxyserver, extracting profile information added to the data request by theproxy server, using the extracted profile information to generate aresponse, and sending the response to the proxy server.

In general, in another aspect, the invention features a computer programresiding on a computer-readable medium. The program includesinstructions for causing a computer to intercept a data request from aclient computer that is directed to a target server, encrypt profileinformation, augment the data request by adding the encrypted profileinformation to the data request, and send the augmented data request tothe target server. In another aspect, the invention features a computerprogram residing on a computer-readable medium that includesinstructions for causing a computer to receive a data request comprisingencrypted profile information that was added to the data request by aproxy server, extract the profile information added by the proxy server,use the extracted profile information to generate a response, and sendthe response to the proxy server.

In general, in another aspect, the invention features a proxy serverthat includes a database, a network interface, a processor, and amemory. The database includes records storing user profile information.The network interface operatively couples the proxy server to a networkto exchange data with a client computer and with a target server. Theprocessor is operatively coupled to the network interface, the database,and a memory. The memory includes executable instructions for causingthe processor to intercept a data request that is directed to a targetserver, retrieve a record from the database, encrypt profile informationin the record, augment the data request by adding the encrypted profileinformation, and send the augmented data request to the target server

In general, in another aspect, the invention features an informationserver that includes a network interface, a processor, and a memory. Thenetwork interface operatively couples the information server to a proxyserver. The processor is operatively coupled to the network interfaceand to the memory. The memory includes executable instructions forcausing the processor to receive a data request from the proxy server,decrypt user profile information added to the data request by the targetserver; and use the decrypted user profile information to generate aresponse to the data request.

Implementations may include one or more of the following features. Areference token may be exchanged between servers and used to refer topreviously exchanged profile information. The reference token may beplaced in subsequent data request sent by the proxy server to the targetin place of full profile information. The profile information that isencrypted by the proxy server can be stored in proxy server databaserecords. The particular user profile information encrypted and includedin a data request can be selected based on an identity of a clientcomputer user or a browser user. The identity may be determined usingthe Internet Engineering Task Force IDENT protocol or by using anothermethod.

Implementations also may include one or more of the following features.Profile information may be encrypted at the proxy server using a sessionkey as an encryption key, and may be decrypted at the target serverusing the same session key. The session key may be determined by theproxy server and sent to the target server using a public keycryptography algorithm and a public key associated with the targetserver. A data request may use the hypertext transfer protocol. Profileinformation extracted from the data request at the target/informationserver can be provided to a web application, such as a CGI script, thatis used to generate a response.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Implementations mayprovide advantages including reduction of redundant data entry,reduction of user data entry errors, secure storage of user data, andautomated user profile determination and dissemination. Differentencryption keys can be used for different information servers, and eachinformation server may establish characteristics associated with itsencryption key. A web site may dynamically generate, maintain, andchange its unique encryption key. This may help to minimize risk ofreplay attacks, message forgery, and message tampering. In addition,implementations may support multiple levels of security.

Other features, objects, and advantages of the invention will beapparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a computer network diagram.

FIG. 2 is a computer network diagram.

FIGS. 3A and 3B show exemplary HTTP headers.

FIGS. 4A and 4B are flowcharts.

FIG. 5 is a message flow diagram.

DETAILED DESCRIPTION

Processing of an information request at a information server, such as aweb server, can be facilitated by a data transfer mechanism in whichdata needed to process the request is stored at a proxy server andautomatically transferred to the information servers. Such a datatransfer mechanism can be used, for example, by an information serviceprovider (ISP) or on-line service provider (OSP) to automaticallytransfer information about a user (a “user profile”) to affiliated websites. Referring to FIG. 2, to automatically transfer a user profile toa web server 203, the user profile information is first stored at aproxy server 202 in a database 220. When a HTTP data request 211 isreceived by the proxy server 202 from a web browser 201, the userprofile information from database 220 is encapsulated in a request 212that is forwarded by the proxy server to web server 203. The proxyserver 202 encapsulates the user profile information in the request 212by adding HTTP headers containing the user profile information to theheaders received in the request 211.

FIGS. 3A and 3B shows fields in HTTP requests. The fields 300 may befields in a request 211 from a client computer 201, and the fields 350may be fields in a request 212 forwarded by proxy server 202 to a website 203. Referring to FIGS. 3A and 3B, each field 301-303 includes aHTTP field name and a value associated with the field. HTTP field namesidentify the associated field value. For example, the “User-Agent:”field name in field 302 indicates that request 300 originated at a“Mozilla/3.0 compatible” browser; and the “Cookie:” field name in field303 includes the value “been_here_before” is a web cookie. When a HTTPrequest 211 having fields 300 is received at proxy 202, the proxy server202 can add user profile information to the request 211 by addingadditional HTTP fields 304-305 containing the profile information,thereby generating a new request 212 with the user profile informationencapsulated in fields 304-305.

Database 220 may be a local or remote database that can store multipleuser profiles. For example, the database 220 may be a database storinguser profiles on a hard disk directly connected to the proxy server 202,or the database may be a SQL database at a remote system and accessedover a TCP/IP connection. Still other database 220 implementations maybe used. Each user profile may be associated with a particular user orgroup of users. A user profile may be selected from the database 220based on the identifying information associated with a particularcomputer or user of that computer. To determine the user's identity, aproxy server may use a table or database that associates user identityinformation with network connection information. For example, referringto FIGS. 2, 4A, and 4B, when a client computer 201 connects to a network230, the client computer's user may submit name and password informationto a POP or to a login server. The POP or login server may then send theuser name and network connection information unique to that user (suchas a unique combination of TCP/IP address and port number) to the proxyserver 202 where it is stored in a database 220 (step 400). When theproxy server 202 receives a subsequent HTTP request 211 (step 401), theproxy server can identify the user associated with the request byquerying the database of stored name and network connectionassociations. A proxy server also may identify a user using the IDENTprotocol. The IDENT protocol is an Internet protocol that allows acomputer to ask another computer for the name of the user. The IDENTprotocol is further described in Internet Engineering Task Force (IETF)document RFC1413.

When the proxy server 202 has identified the user (step 402), the proxyserver can retrieve a user profile associated with that user from itsdatabase 220. The proxy server may then add HTTP fields containing userprofile information to fields in the original HTTP request 211 (step403). For example, header fields 304-305 may be added to the originalheader fields 301-303 from request 211. Field 304 may includeunencrypted user profile data (“UserName=John_Doe, ZipCode=60609,ParentalControl=YoungTeen), while field 305 may include encrypted userprofile data. Encryption of data in the field 305 may use the SecureDataprotocol (explained later). The proxy server thereby forms the modifiedHTTP request 212 containing the user profile data. The modified request212 may then be forwarded by the proxy server for receipt at a web site(steps 404 and 421).

Particular web servers may or may not be configured to recognize theuser profile data fields 304-305. A web server that is not configured torecognize the user profile fields 304-305 may ignore the fields. A webserver that is configured to recognize the user profile fields 304-305can extract the profile data from the field 304-305 (steps 422 and 424).Extraction of user profile data in the field 305 may include decryptionof the user profile data in encrypted field 305. The extracted userprofile data can be used, for example, to generate or customize datasent in response 213 to the proxy server for forwarding as a response214 to a user or client computer (step 425). For example, a touristinformation web server may customize a page based user profile dataspecifying a browser user's age, and interest. If a web server looks fora user profile field 304-305 in the request 212, and the user profilefield is not present, the server may use “traditional” data inputmechanisms (such as forms and web cookies) to obtain needed data from auser (step 422-423). After the necessary data is obtained, the webserver 203 can generate a response (step 425).

Exchange of user profile data between a proxy server 202 and a webserver 203 may implemented using custom filtering software (“proxy dataexchange filter” software) that can be added to commercially availableproxy and web site server software. For example, Microsoft InternetInformation Server (IIS) provides an application programming interfaceknown as the information server application programming interface(ISAPI) that allows custom filtering software to be added to an IIS website. A Netscape web site server provides an application programminginterface known as the Netscape server application programming interface(NSAPI) that may also be used to develop custom filtering software. Whena request 212 from the proxy server 203 is received at an IIS orNetscape server web site, the request 212 is passed to the proxy dataexchange filter by the IIS or Netscape server software and the userprofile data is extracted from the headers 304-305. The extractedprofile data may then be made available as HTTP environment variables,database entries, or other data exchange structures that can be used byweb applications. The remaining header information in request 212 (e.g.,the original information from request 211), may then be processed by theweb server to obtain response 213 information.

A proxy server 202 and web server 203 may implement the SecureDataprotocol (described below) to encrypt user profile data. Encrypted userprofile data may be indicated by a special HTTP header. For example, thefield name “User-Profile-SecureData” in field 305 indicates that thefield value segment of field 305 contains encrypted profile data.

The SecureData protocol uses multiple cryptography algorithms to providesecure user profile data transfers between a proxy server 202 and a webserver 203. For example, the SecureData protocol may use the Rivest,Shamir, Adelman (RSA) public key encryption algorithm or thepretty-good-privacy (PGP) public key cryptography algorithm along withthe RSA RC4 symmetric encryption algorithm. Additional information onthe RC4 algorithm can be found, for example, in Applied Cryptography,2nd edition, By Bruce Schneier, John Wiley & Sons, 1996.

User profile information may be encrypted at proxy server 202 using asymmetric encryption algorithm. A symmetric encryption algorithm, suchas the RSA RC4 algorithm, uses the same encryption key (referred toherein as a “session” key) to encrypt and decrypt data. The proxy server202 may encrypt user profile data and place it in a HTTP field inrequest message 212. The proxy server 202 can also separately encryptthe session key using a public key cryptography algorithm and the publickey of the web server 203. The public key encrypted session key may alsobe placed in the request message 212, or may be sent separately to theweb server 203. When the web server 203 has received the encryptedsession key and user profile data, the web server 203 can decrypt itssession key by using the public key cryptography algorithm and the webserver's private key. The web server 203 may then decrypt the userprofile information using the decrypted session key. FIG. 5 showsfurther details of an implementation in which a request message mayinclude both the encrypted session key and the encrypted user profiledata.

Referring to FIG. 5, when a request 511 is received at the proxy server502, the proxy server determines whether it should add encrypted userprofile data to the request. To do so, the proxy server may extract adestination web site address from URL information in the request 511,and query a database to determine whether the destination web site is toreceive user profile information and whether the information is to beencrypted. If the destination web site is to receive encrypted userprofile information, the proxy server 502 may then query its database todetermine whether it has a valid public key for the web server 503. Ifthe proxy server 502 has a valid public key, the proxy server can usethe public key to encrypt session key information that can be providedto a symmetric encryption algorithm to encrypt user profile data. Theencrypted session key and user profile data may then be forwarded inrequests 514 to the web server 503.

If the proxy server 502 does not have a valid public key for web server503, the proxy server will obtain the public key from the web server 503using a HTTP request 512. The request 512 includes a URL that identifiesa public key file (“pub_key_file”) stored on the server 503. The publickey file may include additional information used by the proxy server502. For example, the public key file may include the length of thepublic key, a SecureData protocol version number, a list of supportedencryption algorithms, and shortcut configuration information(“shortcut” information is further explained, below).

An exemplary public key may have the format shown below (chevrons and‘<’ and ‘>’ delineate fields in the public key file and brackets and ‘[’and ‘]’ delineate optional information):

Exemplary Public Key File

  <public key = length-of-key key> [<Version = SecureData protocolversion number>] [<crypto = <encryption method>] [<shortcut =[none|low|med|high|max]>]

The web server's public key file is returned to the proxy server 503 ina HTTP response 513. The web server 503 may provide additionalSecureData protocol information in HTTP fields of response 513 and/or inthe public key file returned by the response message 513. For example,HTTP fields in response 513 may specify a time to live (TTL) for thekey. The TTL value can be used to indicate the period during which thepublic key is valid.

A proxy server 502 or web server 503 may check a SecureData protocolversion number returned in the public key file, in request 512 and/or inresponse 513 to ensure that the protocol is functioning properly and torecover from or to avoid errors. For example, if a proxy server 502detects that protocol versions numbers in a retrieved public key fileand those in a header of a response 513 do not match, the proxy servermay re-submit the request 512 to the server 503. When the request 512 isre-submitted, the proxy server 502 can include the HTTP “no-cache”pragma to instruct caching systems between the proxy 502 and the webserver 503 not to use cached data. This may help avoid errors introducedby using stale cached data. When the proxy server 502 has received theweb server's public key, it may cache the public key subject to atime-to-live (TTL) value specified by the web server 503 and/or theproxy server's own TTL policies.

If the proxy server 502 is unable to retrieve a web server's public keyinformation or the public key information is otherwise unusable, theproxy server can add a problem report information to fields in a HTTPrequest 514 to indicate why the public key information is unusable. Forexample, the proxy server may indicate that the key information has beencorrupted or a protocol version number or encryption level specified inthe public key file is not supported. If the a web server's public keyinformation is unusable and, consequently, the SecureData encryptionprotocol cannot be used, a proxy server may continue to forward the HTTPrequests from browser clients to the web server without addingadditional SecureData proxy headers. Alternatively the proxy server mayblock or otherwise filter request to the web server. The specificbehavior may be defined on a per-web server basis using configurationinformation stored at the proxy server 502.

Once the proxy server 502 has the public key of web server 503, theproxy server can use the public key to encrypt session key data. Theencrypted session key data may then be added to HTTP fields in therequest from a browser or client computer 511 to form a modified request514 that includes the public-key-encrypted session key information. Theproxy server also can encrypt the user profile data using the sessionkey information and a symmetric encryption algorithm and place theencrypted user profile data in HTTP fields in the modified request 514.For example, referring to FIG. 3B, the field 305 includes session keydata “session=a3f792b210dafad” that may be public-key encrypted, anduser profile data “Profile=A389C2ZA845MRAS02VMA39v1Z93AYC39AC3ABCEG78BB”that may be encrypted using a symmetric algorithm.

Different web server's or groups of web servers can have differentsession keys. A web server's session key may be formed by combining a“master” session key that is the same for a group of web servers with akey mask that can be used to create a unique session key for a webserver or a group of web servers. For example, a 64-bit master sessionkey may be combined with a 64-bit key mask using an exclusive-or (‘XOR’)operation, to yield a unique 64-bit session key. In someimplementations, the master session key may be the proxy server's publickey. Other methods of generating unique keys can be used. The sessionkey data can in field 305 (e.g., “session=a3f792b210dafad”) can includenumerous sub-fields. For example, the session key data can include amaster key, a key mask, a timestamp, a URL hash, a Proxy IP field, andan encoding scheme field. These fields can contain the following data:

-   Master key: The master key is a value that is generated by the    SecureData proxy server that can be combined with a key mask to    generate a unique session key. The proxy server may periodically    generate a new master session key. For example, a new master session    key may be generated every n minutes. The Master key may be the    proxy server's public key.-   Key mask: The key mask is a value generated by a SecureData proxy    server that is unique to a particular web site and which can be    combined with a master key to generate a unique session key for that    web site. A master key and a key mask can be combined using an    exclusive-or (‘XOR’) operation, by appending the keys together, or    by another key combination algorithm. A new key mask may be    periodically generated. For example, a new key mask may be generated    every n minutes.-   Timestamp: A timestamp value may be added to the public-key    encrypted data to make replay attacks more difficult. The timestamp    value can be checked by the receiving web server and compared to the    current time. If the difference between the timestamp value and    current time exceeds a threshold value, the request may be denied or    other error recovery or security procedures may be employed.-   URL hash: A hash value derived from a requested URL may be added to    the public-key encrypted data to make forging or tampering more    difficult.-   Proxy IP: The IP address of the proxy server be inserted in the    session key data. When a request 514 is received at a web server    503, the web server may compare the IP address in the proxy IP field    to help confirm that the request came from a particular proxy server    502. If the addresses differ, the request 514 may be rejected or    other error recovery or security procedures may be employed.-   Encoding scheme: Encoding scheme data may be sent from the    SecureData proxy server to a SecureData web server to identify how    user profile data is encoded. For example, the encoding scheme value    may indicate that profile data is in a binary (bin) form, or in    name-value pair (nvp) form (which may be expressed using the    Abstract Syntax Notation 1 (ASN.1) or other name-value coding    scheme), or in another form.

The proxy server 502 can use a web server's unique session key toencrypt user profile data that is add it to the field 305. In someimplementations, the user profile data may be placed in one or moreadditional fields. The request 514, now containing the public-keyencrypted session data and the symmetric encrypted user profile data, isthen sent to web server 503.

When request 514 is received by the web server 503, the request can bepassed to to proxy data exchange filter software that can extract theadded fields 304-205 from the request 514, decrypt the session key andthe user profile information contained in the fields 304-205, and makethe user profile information available to web server applications. Theuser profile information may be made available to web serverapplications by setting HTTP environment variables, by storing it in adatabase, by placing it in shared memory, and/or using other dataexchange techniques. The proxy data exchange filter software may thenpass the request 514 back to the web server for further processing andfor generation of a response 515.

The web server 503 can store received profile data in a local databasefor future request processing purposes. The web server 503 may return ashortcut token to the proxy server 502. The proxy server 502 may add theshortcut token to a subsequent request 518 in place of the ‘full’ userprofile data sent in the request 514. This can be used to reduce theamount of data that needs be transferred in subsequent request 518. Ashortcut token can be an index value, database query information, filename, other pointer data, or an arbitrary value generated by the website 503 and used to reference the stored user profile data.

A web server's public key file may be sent to the proxy server 502 usinga security level specified by the site 503. For example, a web site'spublic key file include data indicating that the web site will use aspecified one of the following shortcut key security levels:

-   -   none: If “none” is specified, the shortcut token is sent to the        proxy server as a clear (e.g., unencrypted value).    -   low: If “low” is specified, the shortcut token is sent to the        proxy server as a clear value and is accompanied by a hash of a        previously requested URL.    -   medium: If “medium” is specified, the “low” security level        information is further accompanied by a timestamp value.    -   high: If “high” is specified, the “medium” security information        is further accompanied by the proxy server's IP address.    -   max: If “max” is specified, the “high” security information is        further accompanied by a sequence counter value. The sequence        counter value may be based on a initial URL hash, the key mask,        or other value, and is incremented in subsequent transactions.

At low, medium, high, and max security levels, the shortcut token andrelated security data can be sent in encrypted form using, for example,the proxy server's public key (which may be the master key value).Shortcut token security levels may also be indicated using HTTP fieldsin a response 513 or 515, or may be specified using data stored in aconfiguration database at the proxy server 513 using a data entryterminal.

A proxy server 502 or web server 503 may include other HTTP fields in arequest 512, 514, 518 or in a response 513, 515, 519 to control userprofile data transfers and/or the operation of the SecureData protocol.For example, HTTP fields in requests and/or responses may specify thefollowing directives:

-   Flush=<shortcut value|ALL>: The ‘Flush’ directive can be sent to the    proxy server 502 to discard a specified shortcut token or to discard    all shortcut tokens from a particular web server. The ‘Flush’    directive may also be sent to a web server to cause the web server    to discard stored user profile data associated with a particular    shortcut token or to discard all stored user profile data associated    with the sending proxy server. This directive may be used by a web    server 503 or proxy server 502 that is performing a reset operation.-   WrongKey: The WrongKey directive indicate that improper security    protocol information was received. A proxy server that receives the    WrongKey directive may re-send a request using a HTTP “no-cache”    pragma. The “no-cache” pragma indicates that cached data should not    be used to satisfy the request.-   SendFull: A web server can issue a SendFull directive to indicate    that a proxy server should send “full” user profile data (rather    than a shortcut token) in a subsequent HTTP request.-   TTL=<n>: The TTL (time to live) directive specifies a period (n, in    seconds) during which a shortcut token is valid. Similar directives    may be included in requests or response to indicate time-to-live    values for other data, such as session keys and public keys.

The invention may be implemented in digital electronic circuitry, or incomputer hardware, firmware, software, or in combinations of them.Apparatus of the invention may be implemented in a computer programproduct tangibly embodied in a machine-readable storage device forexecution by a programmable processor; and method steps of the inventionmay be performed by a programmable processor executing a program ofinstructions to perform functions of the invention by operating on inputdata and generating output. The invention may advantageously beimplemented in one or more computer programs that are executable on aprogrammable system including at least one programmable processorcoupled to receive data and instructions from, and to transmit data andinstructions to, a data storage system, at least one input device, andat least one output device. Each computer program may be implemented ina high-level procedural or object-oriented programming language, or inassembly or machine language if desired; and in any case, the languagemay be a compiled or interpreted language. Suitable processors include,by way of example, both general and special purpose microprocessors.Generally, a processor will receive instructions and data from aread-only memory and/or a random access memory. Storage devices suitablefor tangibly embodying computer program instructions and data includeall forms of non-volatile memory, including by way of examplesemiconductor memory devices, such as EPROM, EEPROM, and flash memorydevices; magnetic disks such as internal hard disks and removable disks;magneto-optical disks; and CD-ROM disks. Any of the foregoing may besupplemented by, or incorporated in, specially-designed ASICs(application-specific integrated circuits).

A number of embodiments of the present invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, server, proxy, and client protocols need not use the HTTPprotocol. Alternate protocols and data formats may be used such as filetransfer protocol (FTP) or network news transfer protocol (NNTP).Accordingly, other embodiments are within the scope of the followingclaims.

What is claimed is:
 1. A method comprising: identifying an initialrequest from a user, the initial request being generated at a clientapplication; extracting information associated with the user from theinitial request; decrypting the extracted information that is encryptedby an encryption algorithm; storing the information in a non-transitorystorage medium; creating, by at least one processor, a token thatreferences the stored information; returning the token in response tothe initial request; receiving the token in a subsequent request via anAPI; accessing the information stored in the non-transitory storagemedium using the token; and using, by the at least one processor, theaccessed information to generate a response to the subsequent request.2. The method as recited in claim 1, wherein the subsequent request isreceived from an intermediary server.
 3. The method as recited in claim1, further comprising associating a time to live value with the token,the time to live value specifying a time period during which the tokenis valid.
 4. The method as recited in claim 3, wherein the informationin the initial request is encrypted within a header of the request. 5.The method as recited in claim 4, wherein the initial request comprisesan HTTP request.
 6. The method as recited in claim 4, wherein theinformation is encrypted using a symmetric encryption algorithm.
 7. Themethod as recited in claim 5, further comprising determining an IPaddress of a client computer including the client application at whichthe initial request was generated; and querying a database to determinean identity associated with the IP address in the database.
 8. Themethod as recited in claim 7, further comprising: extracting anencrypted key from the initial request; decrypting the encrypted key;and using the decrypted key to decrypt the information extracted fromthe initial request.
 9. The method as recited in claim 8, whereindecrypting the encrypted key comprises decrypting the encrypted keyusing a public key algorithm and a private key.
 10. The method asrecited in claim 1, further comprising encrypting the token.
 11. Themethod as recited in claim 10, further comprising associating a sequencecounter value with the token.
 12. The method as recited in claim 10,further comprising associating a time to live value with the token. 13.The method as recited in claim 1, further comprising: receiving a flushdirective, the flush directive referencing the token; and discarding theinformation referenced by the token upon receiving the flush directive.14. A method comprising: receiving, at a first server, an initialrequest; obtaining, using the first server, user information from theinitial request; decrypting the user information that is encrypted by anencryption algorithm; storing the user information in a non-transitorystorage medium; returning an identifier in response to the initialrequest; receiving a subsequent request including the identifier via anAPI; retrieving the stored user information using the identifier; andusing, by the first server, the retrieved user information to generate aresponse to the subsequent request.
 15. The method as recited in claim14, wherein the initial request is addressed to the first server. 16.The method as recited in claim 15, wherein the initial requestoriginated at a client device.
 17. The method as recited in claim 16,wherein the initial request is an HTTP request.
 18. The method asrecited in claim 16, wherein the initial request is received via an API.19. The method as recited in claim 16, wherein the subsequent request isreceived from a second server in communication with the client device.20. The method as recited in claim 19, further comprising sending theresponse to the subsequent request to the second server.
 21. The methodas recited in claim 20, wherein the response is sent to the secondserver via an API.
 22. The method as recited in claim 20, wherein theuser information comprises demographic information about a user.
 23. Themethod as recited in claim 22, wherein the information is encryptedusing a symmetric encryption algorithm.
 24. The method as recited inclaim 22, further comprising encrypting the identifier.
 25. The methodas recited in claim 24, wherein the identifier comprises a token. 26.The method as recited in claim 25, further comprising associating asequence counter value with the token.
 27. The method as recited inclaim 25, further comprising associating a time to live value with thetoken.
 28. The method as recited in claim 25, further comprising:receiving a flush directive, the flush directive referencing the token;and discarding the user information referenced by the token uponreceiving the flush directive.
 29. A system comprising: at least oneserver; a non-transitory storage medium storing instructions, that whenexecuted by the at least one server, cause the system to: identify aninitial request from a user, the initial request being generated at aclient device; extract information associated with the user from theinitial request; decrypt the information that is encrypted by anencryption algorithm; store the information in the non-transitorystorage medium; return a token that references the stored information inresponse to the initial request; identify the token in a subsequentrequest received via an API; access the information referenced by thetoken stored in the non-transitory storage medium; and use the accessedinformation to generate a response to the subsequent request.
 30. Thesystem as recited in claim 29, wherein the initial request is addressedto the at least one server.
 31. The system as recited in claim 30,wherein the initial request is an HTTP request.
 32. The system asrecited in claim 30, wherein the initial request is received via an API.33. The system as recited in claim 30, wherein the subsequent request isreceived from a second server in communication with the client device.34. The system as recited in claim 33, wherein the instructions, whenexecuted by the at least one server, cause the system to send theresponse to the subsequent request to the second server.
 35. The systemas recited in claim 29, wherein the information in the initial requestis encrypted using a symmetric encryption algorithm.
 36. The method asrecited in claim 25, wherein the instructions, when executed by the atleast one server, cause the system to associate a sequence counter valuewith the token.
 37. The method as recited in claim 25, wherein theinstructions, when executed by the at least one server, cause the systemto associate a time to live value with the token.
 38. The method asrecited in claim 25, wherein the instructions, when executed by the atleast one server, cause the system to encrypt the token.